ADA, SERUM in Dehradun

What is a ADA, SERUM?

Adenosine deaminase is an enzyme concentrated in lymphocytes, particularly the T cells that mount the immune response to tuberculosis. Its level rises where those cells are active in large numbers, which is why it became a marker for tuberculous inflammation. The critical point about ADA is where it is measured. In body fluids, notably pleural fluid in suspected tuberculous pleural effusion and ascitic fluid in suspected tuberculous peritonitis, a raised ADA has good diagnostic value and is genuinely useful, because obtaining bacteriological proof from those fluids is difficult, cultures take weeks and are frequently negative even in real disease. In serum it is far less informative: a raised level indicates lymphocyte activation of some kind, which occurs in many infections, in lymphoma and in liver disease, and it is not specific for tuberculosis. Serum ADA is therefore a supporting marker at best, and it should never be used alone to start or withhold tuberculosis treatment, which is a decision with months of consequences.

Why take this test?

Serum ADA is ordered as a supporting investigation where tuberculosis is being considered and other results are being assembled: prolonged fever, night sweats, unexplained weight loss, or a chronic cough, particularly in India where tuberculosis remains common. Its more valuable use is on body fluid rather than blood, and if a pleural effusion or ascites has been found, ask your doctor whether ADA on the fluid is appropriate, since that is where the test performs. It is also sometimes used to follow response in established disease. Whatever it shows, it belongs alongside the definitive tests: a chest X-ray, sputum examination and, most importantly, a molecular test such as MTB/RIF which detects the organism directly and reports rifampicin resistance. Tuberculosis treatment lasts months and carries real side effects, so the diagnosis should rest on direct evidence wherever it can be obtained, with ADA contributing rather than deciding.

• Suspected tuberculosis with prolonged fever, night sweats or weight loss
• As a supporting marker alongside chest X-ray and molecular testing
• Far more valuable on pleural or ascitic fluid than on serum
• Suspected tuberculous pleural effusion or peritonitis, on the fluid
• Following response in established disease
• Never sufficient alone to start or withhold TB treatment

FAQs: ADA, SERUM in Dehradun